This invention relates to a connecting device, more particularly to a connecting device for connecting a fan blade to a ceiling fan rotor.
Ceiling fans have been popular for many years. However, conventional ceiling fans typically are not convenient to install. If the fan blades are not installed properly, the fans tend to vibrate and create a significant amount of noise. Referring to FIG. 1, a conventional ceiling fan 10 is shown to include an outer casing 12 for housing a motor 14, a plurality of fan blades 16 (only one is shown), and a plurality of mounting arms 18 (only one is shown) for connecting the fan blades 16 to the bottom of the motor""s rotor 20. Each mounting arm 18 has two ends which are respectively secured on the corresponding fan blade 16 and the bottom of the rotor 20 by screw fasteners 22, 24.
The use of screw fasteners 22, 24 tend to make if inconvenient to assemble the mounting arms 18. Insufficient tightening of the screw fasteners 22, 24 can result in vibration of the mounting arms 18 and even discharge of the fan blades 16 from the rotor 20 during operation. Dynamic imbalance and vibration can even occur when screw fasteners 22, 24 are tight, but tightened in the wrong order. These variables can be frustrating for the do-it-yourself homeowner that simply wants to install a ceiling fan.
Recent fans have been designed to make it easier for the do-it-yourself installer. One such fan is disclosed in U.S. Pat. No. 6,095,753 to Hsu, and has a structure for mounting ceiling blades that does not require screws for attaching the blade to a ring mount on the rotor. The ring mount has a plurality of recesses having an inner end that gradually decreases in width toward an outer end. Each blade has a tongue that is configured so that its outer end is the same width as the outer end of a corresponding recess. The tongue inner end is also configured so that its width is the same size as the inner end of the corresponding recess. The blades slidingly connect to the rotor without the use of tools, and centrifugal force keeps the blades from being dislodged during operation. When the fan is not in motion, the blades can be removed by sliding each blade toward the inner end of a corresponding recess. While this is a convenient connection with respect to ease of assembly and disassembly, it requires exact tolerances for parts. If the tongue and recess do not fit together properly, then annoying and possibly dangerous blade vibration can occur.
Another such fan is disclosed in U.S. Pat. No. 5,980,353 to Wu. This fan also requires close tolerances so that the plug end of the blade does not vibrate with respect to the insert slot. Further, vibration can occur if each rotor mounting segment is not fastened properly to the motor or motor casing.
Accordingly, a need exists for ceiling fan having a simple attachment mechanism for attaching the fan blades to the rotor without using tools that can be manufactured without meeting exact tolerances.
The present invention comprises an impeller and blade assembly. A ring, including a plurality of dovetailed recesses that have a ceiling and two side walls is mounted onto the impeller. A biasing member such as a spring is secured to each recess""s ceiling. Each fan blade is constructed from a wing connected to an arm, that has a dovetailed tongue corresponding to one of the recesses. Each tongue can be made to engage one of the dovetailed recesses without the use of a tool. The biasing member provides a bias between the tongue and recess sidewalls to prevent undue vibration therebetween. The biasing member or spring also locks the tongue into the recess to prevent accidental radial displacement. Thus, a tongue cannot move in a substantially radial direction with respect to the ring without applying pressure to the spring. The advantage of this invention is quick and easy installation, and increased safety and satisfaction due to reduced vibration.